A commonly used adapter for field-connection to catheters is an adapter which includes a cup-shaped female member having an internal thread, an externally threaded male member for threaded engagement with the cup-shaped member which is characterized by an axially bored nose portion, and an axially bored resilient grommet disposed therebetween. The end of a catheter is inserted into the nose portion of the male member and into the grommet when the two threaded members are in a loosened mode. When the male member is threadedly tightened into the cup-shaped member, the configuration thereof and that of the grommet are such that the grommet is compressed onto the portion of the catheter extending therethrough to provide a retention force on the catheter. Finger-engageable members may be provided on the sides of the nose portion of the male member to facilitate tightening same into the cup-shaped member. One problem is occlusion of the catheter if the compression forces thereon are too great. The smaller the diameter of the catheter the greater is this danger of occlusion so it is a particular problem with the relatively tiny spinal catheters wherein the outer diameter may be in the order of only 0.010- 0.015 inches.
So it is most difficult to tighten the threaded members of such an adapter sufficiently to provide a suitable retention force against an axial force applied to a catheter, particularly one of the smaller ones, without occluding the catheter. Either occlusion of the catheter or separation of same from the adapter could be critical as to the welfare of a patient.